Phosphor deposition system for leds

ABSTRACT

A method to produce a light-emitting device package includes mounting junctions on pads of a metalized substrate, where the junctions are at least partially electrically insulated from each other, and forming wavelength converters, where each wavelength converter is located over a different junction and separated by a gap from neighboring wavelength converters.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation application of U.S. patentapplication Ser. No. 15/857,153 filed on Dec. 28, 2017, which is anational stage entry of International Application No. PCT/EP2016/064987filed on Jun. 28, 2016, which claims the benefit of priority from U.S.Provisional Application No. 62/188,009 filed on Jul. 2, 2015. Each ofthe above applications are incorporated herein by reference in theirentirety.

FIELD OF THE INVENTION

The present disclosure relates to color changing light-emitting devicepackages.

BACKGROUND

Addressable Color Changeable LED Structure

There are several ways to construct a color changing light-emittingdevice package. A number of individual light-emitting diodes (LEDs) ofdifferent colors can be placed under a single primary optic. However,this presents difficulties in mixing the colors. If there is no mixing,some primary optics will project the different colors into differentdirections. When mixing is added, it makes the effective source sizelarger or compromises the design of the primary optics. The result isthat either the beam control is worsened or a larger primary optic isrequired. These affect the overall performance, form factor, and priceof the package.

Alternatively, a number of individual LEDs of different colors can beeach placed under its own primary optic. In this case, the beams may notcompletely overlap, especially at close distances. This can create acolor artifact near the border of shadows. Also, this introduces alimitation on the optical design. More than one primary optic is neededand this may not be preferred aesthetically. This is the currentsolution for color-changing flash modules.

A LED light source based on LED pixels has been discussed for displays,such as a low power addressable LED arrays for color changeabledisplays. U.S. Pat. No. 9,041,025 discloses LED pixels arranged ingroups of four pixels, with the LEDs emitting a single color of lightfor all pixels. A mold positioned over the LED pixels accepts phosphorsfor the individual LED pixels in each group. The phosphors in the moldtransmit at least three (3) primary colors for respective ones of theLED pixels in each group. A fourth LED pixel in the group can transmitwhite light.

High Power Addressable LED Structure

A LED light source based on addressable individual or groups of LEDpixels that can be turned on or off has been discussed.

A number of individual LEDs can be placed near each other in an array,each under their own primary optic. However, this requires a largenumber of LEDs and primary optics, and will take a lot of space.

Osram's Micro Advanced Forward-lighting System (μAFS) concept disclosesa multi pixel flip chip LED array directly mounted to an active driverintegrated circuit (IC). A total of 1024 pixels can be individuallyaddressed through a serial data bus. Several of these units can beintegrated in a prototype headlamp to enable advanced light distributionpatterns in an evaluation vehicle.

Vehicle manufacturers have realized the advantages of selectivelyaddressable LED arrays for headlights. For example, U.S. Pat. No.8,314,558 discloses a vehicle headlamp having a plurality of LEDspositioned into an array. The array has at least one row and at leasttwo columns with each LED positioned at an intersection of a row and acolumn. A LED is illuminated by selectively applying a signal to the rowand a signal to the column corresponding to the position of the LED.

High Tuneability LEDs with Phosphors Deposited on Wafer

It is difficult to coat different types of phosphors on LED pixels onthe same wafer or tile when the LED pixels are in close proximity toeach other. Phosphors for one LED pixel may spill over and mix withphosphors of a neighboring LED pixel. Furthermore, light crosstalkbetween phosphors of neighboring LED pixels varies the color endpointsbetween packages and reduces the range of color tuneability between thecolor endpoints.

Improved Phosphor Deposition System for LEDs

The use of multi-chip LED fixtures to improve color intermixing has beendiscussed. For example, Acclaim Lighting describes a color mixingapplication using a single lens to produce a homogenized beam withblended color and minimal color halos or shadowing. Such multi-chippackages are available from Cree, Osram, Prolight Opto Technology, andOpto Tech Corp.

SUMMARY

Addressable Color Changeable LED Structure

Some examples of the present disclosure provide a color changinglight-emitting device package. Since there is only one LED die in thepackage, only one optic is needed.

The LED die is made of a number of segments, each emitting a differentcolor of light. The amount of light emitted from each segment can bechanged. The result is a change in the average color of the whole LEDdie. The segments are placed close together to enable efficient colormixing in the optic outside of the LED die. This means that betteroptical control can be achieved with a smaller optic, which reduces costand form factor.

The segments can consist of a single junction or multiple junctions. Ina simple example, a LED die is divided into two segments of differentcolors, each consisting of an individually controlled junction. In amore complicated example, a LED die is divided into two segments ofdifferent color, each consisting of nine (9) junctions in parallel or inseries.

The multiple junctions in a single segment can be continuous ordiscontinuous. For example, in the case of two different color segmentseach consisting of nine (9) individual junctions, the junctions ofdifferent segments (colors) may be interspersed (placed among eachother) randomly or in a regular pattern. A regular pattern may be acheckerboard pattern with alternating color junctions, serpentinesegments that spiral outward and encircle each other, or concentriccircular segments of different (alternating) color junctions.

The segments define the borders of the color tuneable region of the LEDdie. If there are two segments of different colors, then the averagecolor can be tuned to either of these endpoint colors or any color on astraight line between the endpoint colors. If there are three segmentsof different colors, the color gamut is defined by a triangle withcorners having the colors of the individual segments. More segments willresult in more shapes in the color space. In some examples, each segmentmay have a different spectral content. This means that all segments mayhave the same color but some might have different color rendition index(CRI) or R9 (red) values.

The junctions of each color should be small and preferably interspersedrandomly or in a regular pattern. From an application's viewpoint, it isbetter to have the colors interspersed like a checkerboard, rather thanhave a few large junctions of all one color. The size of a singlejunction of a color segment should be small. From an application'sviewpoint, it is better to have the LED die divided into a 50×50checkerboard grid of two colors than a 2×2 grid of two colors. On theother hand, the grid with fewer, larger elements is easier tomanufacture. In some examples, an LED die includes individual coloredjunctions of about 50 to 200 micrometers (μm) in width/height and has agrid size on the order of 4 to 20 elements×4 to 20 elements. In otherexamples, an LED die includes individual colored junctions of about 50to 500 μm in width/height. The size or number of individual junctionsdoes not need to be uniform.

The electrodes of the LED die are routed to the perimeter, where theycan be accessed by one or more drivers. There are a number of ways towire this.

The junctions may share a common cathode. The anode of each junction isindividually routed to the perimeter. The cathode connection can be madeon the LED level (when the junctions are not physically separated) or onthe package level.

The junctions may share a common anode. The cathode of each junction isindividually routed to the perimeter. The anode connection can be madeon the LED level (when the pixels are not physically separated) or onthe package level.

All the junctions may be connected in series. The traces that connecteach pair of junctions are also routed to the perimeter, as well as thetwo unpaired connections. In this way, any junction can be shorted out,turning it off. Dimming can still be achieved with a pulse widthmodulation scheme.

One group of junctions may be connected using any of the above methods,and other groups are separately connected using any of the abovemethods. For example, the first row of junctions can be connected inseries, and the second row of junctions can also be connected in seriesbut in a different string.

All of the above routing may apply to the LED die as a whole, or mayapply to the junctions of a certain segment (color). For instance, allof the junctions of one color may be in a series string, and all of thesegments of a different color may be in a separate series string.

All LED junctions of a certain segment (color) may be connected inparallel. For instance, all of the junctions of color 1 can be in asingle parallel string, and the junctions of color 2 can be a separateparallel string.

All traces are routed to the perimeter. This offers ultimate driverflexibility, since any of the above configurations can be made outsideof the package.

High Power Addressable LED Structure

Some examples of the present disclosure provide a light-emitting devicepackage with a single LED die having addressable junctions. Eachjunction can be addressed either individually or in groups (segments).The junctions can be independently turned on, turned off, or “dimmed” toan intermediate value. This enables beam steering, spot reduction,highlighting and dynamic effect features.

When the source package is imaged through a secondary imaging optic, thebeam pattern is changed. The changing beam pattern can be used in anumber of ways. The beam can be steered from one location to another.Parts of the beam can be turned up to highlight a location. Parts of thebeam can be turned down or off to reduce or eliminate light in a placewhere it is not wanted. For instance, parts of the beam can be turneddown or off to reduce glare. It can also save energy by only generatingthe light that is needed. A dynamic effect can be created. This mayhighlight something, illuminate a moving object, or may be used forartistic effect.

The junctions may be completely isolated from each other, or they canshare a common cathode or common anode.

The junctions are arranged as closes as possible while still enablingphosphor deposition with an acceptable amount of phosphor spill-overfrom adjacent junctions and light crosstalk. For example, the activeregions of two adjacent junctions are 1 to 100 μm apart, such as 37.9 μmapart in one direction and 25.9 μm apart in an orthogonal direction.This may be accomplished by attaching the junctions at once, as amonolithic array, still all joined together. The junctions may beseparated after the attach process, such as through a laser-liftoff oftheir growth substrate.

The array may be used as-is or a wavelength converting layer can beapplied. This may be used to make an array of white pixels.

Traces to the junctions are routed to the perimeter, where they may beaccessed by one or more drivers.

As described above, some examples of the present disclosure enable lowcost beam steering without requiring large separate packages withindividual optical elements. The light-emitting device package allowsthe use of a ceramic substrate, which provides more freedom in choosingthe cost, thermal expansion coefficient (influencing integration into asystem), thermal resistance, and mechanical robustness.

Some examples of the present disclosure use smaller numbers of LEDs toachieve a pixilated light source. For instance, if one desires 18pixels, the discrete LED case will require 18 LEDs. If each LED must be0.5 mm², then the total LED area is 9 mm². Compare this to a singlemulti junction LED of only 2 mm².

Some examples of the present disclosure use fewer optics, fewer attachsteps, and fewer optic alignment steps. There is one LED die attach andone optic, compared to many LEDs to attach and many optics. This alsoresults in a lower cost for the light-emitting device package,especially in cases where large numbers of LED dies would result inunder-driving the LEDs.

The size of the optics and source is also smaller. In the discrete LEDcase, a large array of optics is required whereas the light-emittingdevice package uses only one optic. The size of the optic may be largerthan what is required for a single standard LED but it is not as largeas the array of optics. In some applications, there is not enough spacefor a large array of optics. In some applications, there is an aestheticvalue in reducing the size of the combined optics.

High Tuneability LEDs with Phosphors Deposited on Wafer

Some examples of the present disclosure provide discrete strings, lines,or blocks of a transparent conductor such as antimony tin oxide (ATO),indium tin oxide (ITO), or silver nanowires capable of being depositedon a growth substrate of an LED die with multiple junctions. Eachgrouping of transparent conductor can be deposited in separate, distinctlines or blocks. Complex curved, circular, or winding layouts arepossible.

With application of a voltage to a particular transparent conductorstring, phosphors may be electrophoretically deposited only on thetransparent conductor. Varying voltage duration will correspondinglyvary amount and thickness of deposited phosphors.

Separation of phosphor lines may be adjusted by increasing or decreasingwidth of underlying transparent conductor string.

Some examples of the present disclosure provide for low cost wafer leveldeposition of phosphors on sapphire. Multiple types and thicknesses ofphosphors can be used. When singulating the wafer into LED dies,variation due to phosphor crosstalk is minimized to improve colortuneability.

Improved Phosphor Deposition System for LEDs

In some examples of the present disclosure, phosphors are applied byelectrophoretic deposition (EPD) to specific junctions. A voltage can beapplied to specific groups of electrically connected junctions. Discretestrings, lines, blocks, complex curves, circular, winding, orcheckerboard layouts are possible. Varying the voltage during thedeposition or the duration of the deposition may correspondingly varyamount and thickness of deposited phosphors.

To reduce risk of electrical sparking between closely spaced junctionsduring EPD, adjacent junctions can be held at a non-zero voltage. Forexample, a first string of junctions can be held at 800 volts during EPDwhile adjacent junctions are held at 400 volts rather than 0 volts.

If a sharp transition in amount, type, or thickness of phosphor isdesired between closely spaced junctions, adjacent junctions can also beheld at opposite voltage during EPD. For example, a first string ofjunctions can be held at 800 volts during EPD while adjacent junctionsare held at −400 volts rather than 0 volts.

In some examples, antishock or insulating layers can be depositedbetween junctions prior to high voltage EPD.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1-1 is a top view of a light-emitting diode (LED) die in someexamples of the present disclosure.

FIG. 1-2 is a cross-sectional view of the LED die of FIG. 1 in someexamples of the present disclosure.

FIGS. 2 and 3 illustrate the assembly of a light-emitting device packagein some examples of the present disclosure.

FIG. 4 is a top view of a metalized substrate in some examples of thepresent disclosure.

FIG. 5 illustrates in phantom the placement of junctions in the LED dieof FIG. 1-2 on pads of the metalized substrate of FIG. 4 in someexamples of the present disclosure.

FIG. 6 is a top view of a metalized substrate in some examples of thepresent disclosure.

FIG. 7 illustrates in phantom the placement of junctions in the LED dieof FIG. 1-2 on pads of the metalized substrate of FIG. 6 in someexamples of the present disclosure.

FIG. 8 is a top view of a metalized substrate in some example of thepresent disclosure.

FIG. 9 illustrates in phantom the placement of junctions in the LED dieof FIG. 1-2 on pads of the metalized substrate of FIG. 8 in someexamples of the present disclosure.

FIG. 10 is a cross-sectional view of a LED die in some examples of thepresent disclosure.

FIG. 11 is a cross-sectional view of a LED die in some examples of thepresent disclosure.

FIG. 12 illustrates in phantom the placement of junctions in the LED dieof FIG. 10 or 11 on the pads of the metalized substrate of FIG. 4 insome examples of the present disclosure.

FIG. 13 illustrates in phantom the placement of junctions in the LED dieof FIG. 10 or FIG. 11 on the pads of the metalized substrate of FIG. 6in some examples of the present disclosure.

FIG. 14 illustrates a pattern of transparent conductors on a growthsubstrate for forming wavelength converters using electrophoreticdeposition (EPD) in some examples of the present disclosure.

FIG. 15-1 illustrates another pattern of transparent conductors on agrowth substrate for forming wavelength converters using EPD in someexamples of the present disclosure.

FIG. 15-2 illustrates wavelength converters having smaller footprintthan the underlying junctions in some examples of the presentdisclosure.

FIG. 15-3 illustrates wavelength converters of different colors abuttingeach other in some examples of the present disclosure.

FIG. 16 is an International Commission on Illumination (CIE) 1976 colorchart illustrating a hypothetical color tuning range of the LED die ofFIG. 1-2 having cool-white and warm-white phosphor layers in someexamples of the present disclosure.

FIGS. 17 and 18 are top and bottom views, respectively, of a metalizedsubstrate in some example of the present disclosure.

FIGS. 19-1 and 19-2 illustrate the placement of junctions in the LED dieof FIG. 1-2 on the metalized substrate of FIG. 17 in some examples ofthe present disclosure.

FIG. 20 illustrates electrically connected strings of a metalizedsubstrate that is a variation of the metalized substrate of FIG. 17 insome examples of the present disclosure.

FIG. 21 is a flowchart of a method for making a light-emitting devicepackage in examples of the present disclosure.

FIG. 22 is a flowchart of a method for making a LED die in examples ofthe present disclosure.

FIG. 23 illustrates applications of the light-emitting device package ofFIG. 3 in examples of the present disclosure.

Use of the same reference numbers in different figures indicates similaror identical elements.

DETAILED DESCRIPTION

FIG. 1-1 is a top view of a light-emitting diode (LED) die 100 in someexamples of the present disclosure. LED die 100 may be a segmented ormulti junction LED die. LED die 100 includes an array of junctions102-1, 102-2, . . . , and 102-n (collectively as “junctions 102” orindividually as a generic “junction 102”) formed on a growth substrate104. The array of junctions 102 in LED die 100 is not limited to anysize or shape. Trenches 106 down to growth substrate 104 surroundjunctions 102 to completely electrically insulate them from each other.Trenches 106 may be formed by wet etch, dry etch, mechanical saw, laserscribe, or another suitable technique.

FIG. 1-2 is a cross-sectional view of LED die 100 in some examples ofthe present disclosure. Each junction 102 has a semiconductor structureincluding an active region 108 between an n-type semiconductor layer 110and a p-type semiconductor layer 112. Each junction 102 has a cathode114 coupled to its n-type semiconductor layer 110 by an ohmic p-contactthrough an opening in an insulator (dielectric) layer, and each junction102 has an anode 116 coupled to its p-type semiconductor layer 112 by anohmic n-contact through an opening in the insulator layer. Surfacetreatment may be performed on growth substrate 104, such asphotoelectrochemical (PEC) etching or mechanical roughening, or a thinfilm of anti-reflective coating may be applied. In some examples, growthsubstrate 104 is removed from LED die 100 after LED die 100 is mountedon another mechanical support.

LED dies 100 are formed on a growth wafer. The layers for thesemiconductor structure of LED dies 100 are grown on the growth wafer,followed by the ohmic contacts and then the cathodes and the anodes.Trenches 106 are formed in these layers down to the growth wafer tocreate junctions 102 in each LED die 100. Individual LED dies 100 aresingulated from the resulting device wafer.

LED die 100 includes individual wavelength converters 118. Wavelengthconverters may be phosphor layers or ceramic phosphor plates. Eachwavelength converter 118 is located over a different junction 102.Wavelength converters 118 are formed on growth substrate 104 or directlyon junctions 102 when growth substrate 104 has been removed from LED die100 after LED die 100 is mounted on another mechanical support.Wavelength converters 118 are made of a number of different materials togenerate different colors of light, such as whites of differentcorrelated color temperatures (CCTs) or primary colors of red, green,and blue. Instead of individual wavelength converters 118, a singlecontinuous wavelength converter of the same material may be used togenerate a single color of light. Wavelength converters 118 may also beomitted so junctions 102 emit their native color(s) of light based ontheir bandgap energies.

Wavelength converters 118 may be formed on the growth wafer before LEDdies 100 are singulated from the device wafer, or on growth substrates104 after LED dies 100 are singulated from the device wafer.Alternatively, wavelength converters 118 are formed directly onjunctions 102 in LED dies 100 after growth substrates 104 have beenremoved from LED dies 100 after LED dies 100 are mounted on othermechanical supports.

FIGS. 2 and 3 illustrate the assembly of a monochromatic or colorchanging light-emitting device package 300 in some examples of thepresent disclosure. Package 300 includes a LED die 100, a metalizedsubstrate 202, and a primary optic 204. LED die 100 is mounted onmetalized substrate 202, and primary optic 204 is mounted over LED die100 on metalized substrate 202. Instead of mounting LED die 100 onmetalized substrate 202, individual junctions 102 singulated from adevice wafer maybe picked and placed on metalized substrate 202.

Metalized substrate 202 is a single-layer or multi-layer tile, which maybe made of aluminum nitride ceramic, aluminum oxide ceramic, or anothersuitable material. Metalized substrate 202 has a top surface 206, toppads 208 on top surface 206, top traces 210 on top surface 206, and abottom surface 212. Top pads 208 are arranged about the center of topsurface 206 to receive the electrodes (cathodes 114 and anodes 116) ofjunctions 102 in LED die 100. Cathodes 114 and anodes 116 are attachedto top pads 208 by gold-gold interconnect, large-area gold-goldinterconnect, solder, or another suitable interconnect. Top traces 210connect to top pads 208 and fan out to the perimeter of metalizedsubstrate 202 where top traces 210 can be connected to external drivingcircuitry. Top traces 210 may connect certain top pad 208 from differentjunctions 102 in series, in parallel, or a combination thereof.

When metalized substrate 202 is a multi-layer tile, it may includebottom pads 214 on bottom surface 212 and vias 216 that connect top pads208 to bottom pads 214. Metalized substrate 202 may also include lowerlevel (buried) traces 218 and vias 220 that connect top pads 208 totraces 218. Traces 218 may connect certain top pad 208 from differentjunctions 102 in series, in parallel, or a combination thereof. Traces218 may also fan out to the perimeter of metalized substrate 202 wherethey can be connected to external driving circuitry.

Primary optic 204 is a silicone hemispheric lens or flat window moldedover LED die 100 on metalized substrate 202. Alternatively, primaryoptic 204 is a preformed silicone or glass hemispheric lens or flatwindow mounted over LED die 100 on metalized substrate 202. Primaryoptic 204 may include scattering particles. Although shown mounted onmetalized substrate 202, primary optic 204 may be spaced apart frommetalized substrate. Typically, the primary optic is used to tune lightextraction efficiency and radiation pattern of an LED. For a colorchanging light-emitting device package, the primary optic may also beused to tune the color saturation and color cross-talk of the package.For example, while a hemispheric lens may extract more light from LEDdie 100, a flat window may create a more saturated color by recyclingmore of the pump (e.g., blue) light from LED die 100 through wavelengthconverters 118. Primary optic 204 may be shaped to increase colorsaturation and reduce cross-talk between wavelength converters 118 ofdifferent materials. In some examples, primary optic 204 may be a beamhomogenizer, such as a microlens array.

FIG. 4 is a top view of a metalized substrate 400 in some examples ofthe present disclosure. Metalized substrate 400 may be metalizedsubstrate 202 in package 300 (FIG. 3). Metalized substrate 400 is asingle-layer tile. Metalized substrate 400 includes a 6 by 7 array oftop pads 402 (only four are labeled), and top traces 404 connected totop pads 402. Top traces 404 fan out to the perimeter of the metalizedsubstrate 400. To help understand the layout of top pads 402 and toptraces 404, a specific pad is identified by its row and column numbers,and a specific trace is identified by its pad's row and column numbers.For example, the first (leftmost) pad in the first (top) row isidentified as 402(1,1), and the trace to pad 402(1,1) is identified as404(1,1). Cardinal directions are also used to describe the paths of toptraces 404.

In the first row of pads 402, traces 404(1,1) and 404(1,7) fan out tothe west and the east, respectively, toward the perimeter of metalizedsubstrate 400. Traces 404(1,2) to 404(1,6) fan out to the north towardthe perimeter of metalized substrate 400.

In the second row of pads 402, traces 404(2,1) and 404(2,7) fan out tothe west and the east, respectively, toward the perimeter of metalizedsubstrate 400. Trace 404(2,2) fans out diagonally to the northwest andthen to the west to pass between pads 402(1,1) and 402(2,1). Trace404(2,3) fans out to the north, then diagonally to the northwest, andfinally to the north to pass between pads 402(1,2) and 402(1,3). Trace404(2,4) fans out to the north, then diagonally to the northwest, andfinally to the north to pass between pads 402(1,3) and 402(1,4). Trace404(2,5) fans out to the north, then diagonally to the northeast, andfinally to the north to pass between pads 402(1,5) and 402(1,6). Trace404(2,6) fans out diagonally to the northeast and then to the east topass between pads 402(1,7) and 402(2,7).

In the third row of pads 402, traces 404(3,1) and 404(3,7) fan out tothe west and the east, respectively, toward the perimeter of metalizedsubstrate 400. Trace 404(3,2) fans out diagonally to the northwest andthen to the west to pass between pads 402(2,1) and 402(3,1). Trace404(3,3) fans out diagonally to the northwest and then to the north topass between pads 402(2,2) and 402(2,3). Trace 404(3,3) continuesdiagonally to the northwest, to the west to pass between pads 402(1,2)and 402(2,2), diagonally to the northwest, and finally to the north topass between pads 402(1,1) and 402(1,2). Trace 404(3,4) fans outdiagonally to the northeast, to the north to pass between pads 402(2,4)and 402(2,5), and continues to the north to pass between pads 402(1,4)and 402(1,5). Trace 404(3,5) fans out diagonally to the northeast andthen to the north to pass between pads 402(2,5) and 402(2,6). Trace404(3,5) continues diagonally to the northeast, to the east to passbetween pads 402(1,6) and 402(2,6), diagonally to the northeast, andfinally to the north to pass between pads 402(1,6) and 402(1,7). Trace404(3,6) fans out diagonally to the northeast and then to the east topass between pads 402(2,7) and 402(3,7).

Traces 404 for pads 402 in the fourth, the fifth, and the sixth rowsmirror the configuration of traces 404 in the third, the second, and thefirst rows.

FIG. 5 illustrates in phantom the placement of junctions 102 (only sixare labeled for clarity) in LED die 100 on pads 402 (only one islabeled) of metalized substrate 400 in some examples of the presentdisclosure. In this configuration, each junction 102 connects to adifferent pair of pads 402. A dashed line indicates junctions 102 with afirst type of wavelength converters 118 that emits a first color oflight, and a dashed-double dotted line indicates junctions 102 with asecond type of wavelength converters 118 that emits a second color oflight. One or more junctions 102 that have the same type of wavelengthconverters 118 form a segment in LED die 100. Junctions 102 fromdifferent segments (colors) intersperse with each other in a regularpattern, such as in a checkerboard pattern (as shown), serpentinesegments that spiral outward and encircle each other, or concentriccircular segments. Junctions 102 from different segments may alsointersperse randomly.

FIG. 6 is a top view of a metalized substrate 600 in some examples ofthe present disclosure. Metalized substrate 600 may be metalizedsubstrate 202 in package 300 (FIG. 3). Metalized substrate 600 is asingle-layer tile. Metalized substrate 600 includes a 4 by 10 array oftop pads 602 (only six are labeled), and top traces 604 (only six arelabeled) connected to pads 602. Top traces 604 fan out to the perimeterof the metalized substrate 600. To help understand the layout of toppads 602 and top traces 604, a specific pad is identified by its row andcolumn numbers, and a specific trace is identified by its pad's row andcolumn numbers. Cardinal directions are also used to describe the pathsof the top traces 604.

In the first row of pads 602, traces 604(1,1) to 604(1,10) fan out tothe north toward the perimeter of metalized substrate 600.

In the second row of pads 602, traces 604(2,1) to 604(2,10) fan outdiagonally to the northwest and then to the north toward the perimeterof metalized substrate 600. In particular, trace 604(2,2) passes betweenpads 602(1,1) and 602(1,2), trace 604(2,3) passes between pads 602(1,2)and 602(1,3), . . . , and trace 604(2,10) passes between pads 602(1,9)and 602(1,10).

Traces 604 for pads 602 in the third and the fourth rows mirror theconfiguration of traces 604 for pads 602 in the second and the firstrows.

FIG. 7 illustrates in phantom the placement of junctions 102 (only eightare labeled) in LED die 100 on pads 602 (only one is labeled) ofmetalized substrate 600 in some examples of the present disclosure. Inthis configuration, each junction 102 connects to a different pair ofpads 602. A dashed line indicates junctions 102 with a first type ofwavelength converters 118 that emits a first color of light, and adashed-double dotted line indicates junctions 102 with a second type ofwavelength converters 118 that emits a second color of light. One ormore junctions 102 that have the same type of wavelength converters 118form a segment in LED die 100. Junctions 102 from different segments(colors) intersperse with each other in a regular pattern, such as in acheckerboard pattern (as shown), serpentine segments that spiral outwardand encircle each other, or concentric circular segments. Junctions 102from different segments may also intersperse randomly.

FIG. 8 is a top view of a metalized substrate 800 in some example of thepresent disclosure. Metalized substrate 800 may be metalized substrate202 in package 300 (FIG. 3). Metalized substrate 800 is a multi-layertile. Metalized substrate 800 includes a 2 by 6 array of top pads 802and traces 804-1, 804-2, . . . , and 804-8 (collectively “traces 804”)connected to top pads 802. Traces 804 fan out to the perimeter of themetalized substrate. To help understand the layout of metalizedsubstrate 800, a specific pad is identified by its row and columnnumbers. Cardinal directions are also used to describe the paths of thetop traces 804.

In the first row of pads 802, a top trace 804-1 fans out from pad802(1,1) and travels to the north toward the perimeter of metalizedsubstrate 800. A top trace 804-2 has a diagonal portion that connectspads 802(1,2) and 802(2,3), and a straight portion extending from thediagonal portion to the north toward the perimeter of metalizedsubstrate 800. A top trace 804-3 has a diagonal portion that connectspads 802(2,4) and 802(1,5), and a straight portion extending from thediagonal portion to the north toward the perimeter of metalizedsubstrate 800. A top trace 804-4 fans out from pad 802(1,6) and travelsto the north toward the perimeter of metalized substrate 800.

In the second row of pads 802, a top trace 804-5 fans out from pad802(2,1) and travels to the south toward the perimeter of metalizedsubstrate 800. A lower level trace 804-6 has a diagonal portion thatconnects pads 802(2,2) and 802(1,3), and a straight portion extendingfrom the diagonal portion to the south toward the perimeter of metalizedsubstrate 800. A lower level trace 804-7 has a diagonal portion thatconnects pads 802(1,4) and 802(2,5), and a straight portion extendingfrom the diagonal portion to the south toward the perimeter of metalizedsubstrate 800. A top trace 804-8 fans out from pad 802(2,6) and travelsto the south toward the perimeter of metalized substrate 800.

FIG. 9 illustrates in phantom the placement of junctions 102-1, 102-2, .. . , and 102-6 in a LED die 100 on pads 802 (only one is labeled) ofmetalized substrate 800 in some examples of the present disclosure. Inthis configuration, each junction 102 connects to a different pair ofpads 802. A dashed line indicates junctions 102-1, 102-3, and 102-5 havea first type of wavelength converters 118 that emits a first color oflight, and a dashed-double dotted line indicates junctions 102-2, 102-4,and 102-6 have a second type of wavelength converters 118 that emits asecond color of light. Junctions 102-1, 102-3, and 102-5 form a firstsegment in LED die 100 where the junctions connect in series. Junctions102-2, 102-4, and 102-6 form a second segment in LED die 100 where thejunctions connect in series. Junctions 102 from different segments(colors) intersperse with each other in a regular pattern, such as in acheckerboard pattern (as shown), serpentine segments that spiral outwardand encircle each other, or concentric circular segments. Junctions 102from different segments may also intersperse randomly. Any junction 102mounted on a pair of pads 802 in a segment may be bypassed by shortingthe two traces 804 connected to the two pads 802. For example, whenjunction 102-5 in the first segment is to be bypassed, traces 804-2 and804-3 connected to pads 802(2,3) and 802(2,4) may be shorted by anexternal switch (shown in phantom).

FIG. 10 is a cross-sectional view of LED die 1000 in some examples ofthe present disclosure. LED die 1000 is similar to LED die 100 (FIG.1-2) but its junctions 102 share a common cathode 1014, which takes theplace of one junction 102 in the LED die 1000. In LED die 1000, trenches1006 surround junctions 102. Trenches 1006 reach down to an n-typesemiconductor layer 1010 so junctions 102 are only partiallyelectrically insulated from each other as they share a continuous n-typesemiconductor layer 1010. In this configuration, all junctions 102 aredevoid of cathodes 114 (FIG. 1-2).

FIG. 11 is a cross-sectional view of LED die 1100 in some examples ofthe present disclosure. LED die 1100 is similar to LED die 100 (FIG.1-2) except its junctions 102 share a common anode 1116, which takes theplace of one junction 102 in the LED die 1100. In LED die 1100, trenchesare formed around each junction's n-type semiconductor layer 110 andactive region 108. An insulator 1106 fills these trenches before acontinuous p-type semiconductor layer 1112 is formed. Junctions 102 areonly partially electrically insulated from each other as they sharep-type semiconductor layer 1112. In this configuration, all junctions102 are devoid of anodes 116 (FIG. 1-2).

FIG. 12 illustrates in phantom the placement of junctions 102 (only oneis labeled) in a LED die 1000 (FIG. 10) or 1100 (FIG. 11) on pads 402(only one is labelled) of metalized substrate 400 in some examples ofthe present disclosure. In this configuration, each junction 102's anode116 or cathode 114 (FIG. 10 or 11) connects to a different pad 402, andcommon cathode 1014 or common anode 1116 (FIG. 10 or 11) connects to onepad 402. A dashed line indicates junctions 102 with a first type ofwavelength converters 118 that emits a first color of light, and adashed-double dotted line indicates junctions 102 with a second type ofwavelength converters 118 that emits a second color of light. One ormore junctions 102 that have the same type of wavelength converters 118form a segment in LED die 1000 or 1100. Junctions 102 from differentsegments (colors) intersperse with each other in a regular pattern, suchas in a checkerboard pattern (as shown), serpentine segments that spiraloutward and encircle each other, or concentric circular segments.Junctions 102 from different segments may also intersperse randomly.

To help understand the layout of the two serpentine segments, a specificjunction 102 is identified by its row and column numbers. Junctions 102in a first segment (color) may include junctions 102(3,4), (3,5), (4,5),(5,5), (5,4), (5,3), (5,2), (4,2), (3,2), (2,2), (1,2), (1,3), (1,4),(1,5), (1,6), (1,7), (2,7), (3,7), (4,7), and (5,7). Junctions 102 in asecond segment (color) may be made up of the remaining junctions 102.

FIG. 13 illustrates in phantom the placement of junctions 102 (only oneis labeled) in a LED die 1000 (FIG. 10) or 1100 (FIG. 11) on pads 602(only one is labeled) of metalized substrate 600 in some examples of thepresent disclosure. In this configuration, each junction 102's anode 116or cathode 114 (FIG. 10 or 11) connects to a different pad 602, andcommon cathode 1014 or common anode 1116 (FIG. 10 or 11) connects to onepad 602. A dashed line indicates junctions 102 with a first type ofwavelength converters 118 that emits a first color of light, and adashed-double dotted line indicates junctions 102 with a second type ofwavelength converters 118 that emits a second color of light. One ormore junctions 102 that have the same type of wavelength converters 118form a segment in LED die 1000 or 1100. Junctions 102 from differentsegments (colors) intersperse with each other in a regular pattern, suchas in a checkerboard pattern (as shown), serpentine segments that spiraloutward and encircle each other, or concentric circular segments.Junctions 102 from different segments may also intersperse randomly.

FIG. 14 illustrates a pattern 1400 of transparent conductors on growthsubstrate 104, such as a sapphire substrate, for forming wavelengthconverters 118 (FIG. 1-2) using electrophoretic deposition (EPD) in someexamples of the present disclosure. The transparent conductors may beantimony tin oxide (ATO), indium tin oxide (ITO), or silver nanowire.The transparent conductors include blocks 1402 and diagonal lines 1404.Each block 1402 is located over a different junction 102 (only two areshown in phantom) in LED die 100, 1000, or 1100 (FIG. 1-2, 10, or 11).Although shown as squares, blocks 1402 may be other shapes such asrectangles, circles, and ovals. Each block 1402 is separated from itsneighboring blocks 1402 by a gap 1406 in the horizontal direction and agap 1408 in the vertical direction. Lines 1404 connect blocks 1402 toform strings of serially connected blocks 1402, such as diagonal stringsin pattern 1400. Anti-shock or insulating layers may be depositedbetween junctions 102 prior to high voltage EPD.

FIG. 15-1 illustrates another pattern 1500 of transparent conductors ongrowth substrate 104 for forming wavelength converters 118 (FIG. 1-2)using EPD in some examples of the present disclosure. Lines 1404 connectblocks 1402 to form diagonally alternating strings(every-other-junction) in pattern 1500.

For illustrative purposes, assume an LED die 100 includes junctions 102that emit blue light and wavelength converters 118 are cool-white andwarm-white phosphor layers that convert blue light to cool-white andwarm-white colors, respectively. In a first EPD process, a first voltageis applied to a first group of strings in pattern 1400 or 1500 andcool-white phosphors are electrophoretically deposited on the firstgroup of strings. During the first EPD process, a second voltage isapplied to a second group of strings in pattern 1400 or 1500 socool-white phosphors are not formed on the second group of strings. Toreduce the risk of electrical sparking between neighboring strings, anon-zero second voltage is applied to the second group of strings. Forexample, the first voltage may be 800 volts while the second voltage maybe 400 volts. To create a sharp transition in amount, type, or thicknessof phosphor between neighboring strings, a second voltage of theopposite polarity is applied to the second group of strings. Forexample, the first voltage may be 800 volts while the second voltage maybe −400 volts. Alternatively, the second group of strings in pattern1400 or 1500 is not biased but kept floating.

In a second EPD process, a third voltage is applied to the second groupof strings and warm-white phosphors are electrophoretically deposited onthe second group of strings. During this second EPD process, a fourthvoltage is applied to the first group of strings so warm-white phosphorsare not formed on the first group of strings. To reduce the risk ofelectrical sparking between neighboring strings, a non-zero fourthvoltage is applied to the first group of strings. To create a sharptransition in amount, type, or thickness of phosphor between neighboringstrings, a fourth voltage of the opposite polarity is applied to thefirst group of strings. The same or different voltages described for thefirst EPD process may also be used for the second EPD process.Alternatively, the first group of strings in pattern 1400 or 1500 is notbiased but kept floating. Note the EPD processes may be applied on awafer scale to multiple LED dies 100 in a device wafer or individuallyto discrete LED die 100 singulated from the device wafer.

Each phosphor layer (wavelength converter) 118 has sufficient thicknessto fully or substantially convert light entering the phosphor layer 118.The phosphor thickness is controlled by the applied voltage, appliedcurrent, or the applied duration in the EPD process.

The size of phosphor layers 118 may be adjusted by increasing ordecreasing the size of the underlying transparent conductor blocks 1402.The size of the transparent conductor blocks 1402 may be increased tomake the footprint of phosphor layers 118 larger than the underlyingjunctions 102, and the size of the transparent conductor blocks 1402 maybe decreased to make the footprint of phosphor layers 118 smaller thanthe underlying junctions 102 as shown in FIG. 15-2 in some examples ofthe present disclosure. Separation of phosphor layers 118 can beadjusted by increasing or decreasing gaps 1404 and 1406 between theunderlying transparent conductor blocks 1402. By decreasing gaps 1404and 1406, phosphors layers 118 of different colors may abut against eachother as shown in FIG. 15-3 in some examples of the present disclosure.By increasing gaps 1404 and 1406, phosphors layers 118 of differentcolors may be separated by gaps between them.

FIG. 16 is an International Commission on Illumination (CIE) 1976 colorchart illustrating a hypothetical color tuning range of a LED die 100having cool-white and warm-white phosphor layers in some examples of thepresent disclosure. The actual color tuning range of LED die 100 may bedetermined by simulation or experimentation. LED die 100 theoreticallyproduces only a cool-white color at point 1602 when the cool-whitesegment is turned on and the warm-white segment is turned off. LED die100 theoretically produces only a warm-white color at point 1604 whenthe warm-white segment is turned on and the cool-white segment is turnedoff. LED die 100 produces a color along a line 1606 drawn between colorendpoints 1602 and 1604 when a combination of junctions 102 in thecool-white segment and the warm-white segment are turned on. The colorof the blue light emitted by the underlying junctions 102 is indicatedas point 1608.

It may be desired to change color endpoints 1602 and 1604 to moredesirable colors by allowing blue light to leak from junctions 102 inthe cool-white and the warm-white segments. To allow blue light to leakfrom junctions 102 in the cool-white segment, each cool-white phosphorlayer 118 is made with a smaller footprint than its underlying junction102. The ratio of the converted area to the unconverted area, and anyblue light that escapes through the cool-white phosphor layer 118itself, determines the blue light leakage for the cool-white phosphorlayer 118 and sets a new cool-white color with leaked blue light atpoint 1610. Similarly, each warm-white phosphor layer 118 is made with afootprint smaller than its underlying junction 102. The ratio of theconverted area to the unconverted area, and any blue light that escapesthrough the warm-white phosphor layer 118 itself, determines the bluelight leakage for the warm-white phosphor layer 118 and sets a newwarm-white color with leaked blue light at point 1612.

The actual color tuning range of LED die 100 is not between newendpoints 1610 and 1612. This is because the actual color tuning rangeis reduced by crosstalk between neighboring junctions 102 caused by bluelight emitted near the edge of one junction 102 entering anotherjunction's phosphor layer 118 and converting to a different color. Thus,the actual color turning range 1614 is between a cool-white color withleaked blue light and crosstalk at point 1616 and a warm-white colorwith leaked blue light and crosstalk at point 1618. Fortunately, eachphosphor layer 118 only partially covers its underlying junction 102 sothe phosphor layer 118 is separated from its neighboring phosphor layers118. This separation reduces the crosstalk between phosphor layers 118of neighboring junctions 102 and thereby increases the actual colortuning range 1614 of LED die 100.

FIGS. 17 and 18 are top and bottom views, respectively, of a metalizedsubstrate 1700 in some example of the present disclosure, and FIG. 19illustrates in phantom the placement of junctions 102 (only one islabeled) of a LED die 100 (FIG. 1-2) on metalized substrate 1700 in someexamples of the present disclosure. Instead of mounting a LED die 100 onmetalized substrate 1700, individual junctions 102 singulated from adevice wafer may be picked and placed on metalized substrate 1700.Metalized substrate 1700 may be metalized substrate 202 in package 300(FIG. 3). Metalized substrate 1700 is a multi-layer tile. Metalizedsubstrate 1700 is configured to connect junctions 102 of a LED die 100in two segments, such as a cool-white segment and a warm-white segment.Each segment has its junctions 102 connected in parallel, and junctions102 from the cool-white segment and the warm-white segment areinterspersed with each other in regular pattern, such a checkerboardpattern (as shown in FIGS. 19-1 and 19-2), serpentine segments thatspiral outward and encircle each other, or concentric circular segments.Junctions 102 from the cool-white segment and the warm-white segment mayalso interspersed randomly. In other examples, a segment may be asaturated color or pure blue. For example, the two segments may be a redsegment and a green segment.

Referring to FIG. 17, the top surface of metalized substrate 1700includes a 6 by 6 array of top pads 1702 (only two are labeled), and toptraces 1704-1, 1704-2, 1704-3, and 1704-4 (collectively as “traces1704”) connected to top pads 1702. To help understand the layout of toppads 1702, a specific pad is identified by its row and column numbers.Metalized substrate includes vias 1708-1, 1708-2, 1708-3, and 1708-4.Referring to FIG. 18, the bottom surface of metalized substrate 1700includes bottom pads 1706-1, 1706-2, 1706-3, and 1706-4 connected tovias 1708-1, 1708-2, 1708-3, and 1708-4, respectively.

Referring to FIGS. 19-1 and 19-2, trace 1704-1 connects to bottom pad1706-1 (FIG. 17) through via 1708-1. Trace 1704-1 further connects topads 1702(1,1), (1,3), (1,5), (5,1), (4,2), (5,3), (4,4), (5,5), (4,6).With junctions 102 of a LED die 100 mounted on metalized substrate 1700,trace 1704-1 connects anodes 116 of junctions 102 in a first segment inparallel to bottom (anode) pad 1706-1. Junctions 102 in the first (e.g.,warm-white) segment are indicated by a dashed line and have a first typeof wavelength converters 118 that emits a first color of light (e.g.,warm-white).

Trace 1704-3 connects to bottom pad 1706-3 (FIG. 17) through via 1708-3.Trace 1704-3 further connects to pads 1702(6,1), (6,3), (6,5), (3,6),(3,4), (3,2), (2,1), (2,3), (2,5). With junctions 102 of a LED die 100mounted on metalized substrate 1700, trace 1704-3 connects cathodes 114of junctions 102 in the first segment in parallel to bottom (cathode)pad 1706-3.

Trace 1704-2 connects to bottom pad 1706-2 (FIG. 17) through via 1708-2.Trace 1704-2 further connects to pads 1702(1,6), (1,4), (1,2), (4,1),(4,3), (4,6), (5,6), (5,4), (5,2). With junctions 102 of a LED die 100mounted on metalized substrate 1700, trace 1704-2 connects cathodes 114of junctions 102 in a second segment in parallel to bottom (cathode) pad1706-2. Junctions 102 in the second (e.g., cool-white) segment areindicated by a dashed-double dotted line and have a second type ofwavelength converters 118 that emits a second color of light (e.g.,cool-white).

Trace 1704-4 connects to bottom pad 1706-4 (FIG. 17) through via 1708-4.Trace 1704-4 further connects to pads 1702(6,2), (6,4), (6,6), (2,6),(3,5), (2,4), (3,3), (2,2), (3,1). With junctions 102 of a LED die 100mounted on metalized substrate 1700, trace 1704-4 connects anodes 116 ofjunctions 102 in the second segment in parallel to bottom (anode) pad1706-4.

The top surface of metalized substrate 1700 includes bias lines 1710 and1712 connected to vias 1708-2 and 1708-3, respectively. Bias lines 1710and 1712 are used to bias (apply voltage to) the two segments during EPDto form wavelength converters 118.

The top surface of metalized substrate 1700 may include secondary pathsto bias lines 1710 and 1712 to physically reduce the total length ofeach string and therefore reduce total parasitic resistance. Forexample, a trace 1714 (shown in phantom) connects the far end of trace1704-2 to bias line 1710, and a trace 1716 (shown in phantom) connectsthe far end of trace 1704-3 to bias line 1712.

Metalized substrate 1700 may include a transient-voltage-suppression(TVS) diode to each segment. For example, metalized substrate 1700includes a TVS diode 1718 connected to bottom (anode) pad 1706-1 throughtrace 1704-1, and a via 1720 that connects TVS diode 1718 to bottom(cathode) pad 1706-3. Metalized substrate 1700 includes a TVS diode 1722connected to bottom (anode) pad 1706-4 through trace 1704-4, and a via1724 that connects TVS diode 1722 to bottom (cathode) pad 1706-2.

FIG. 20 illustrates electrically connected strings of a metalizedsubstrate 2000 that is a variation of metalized substrate 1700 in someexample of the present disclosure. Metalized substrate 2000 is similarto metalized substrate 1700 except top traces are changed so that eachsegment has three sets of junctions 102 connected in parallel.

In the first (e.g., warm-white) segment, a trace 2004-1 connects via1708-1 to pads 1702(1,1), (1,3), (1,5). Traces 2004-2 connect pad1702(2,1) to pad 1702(3,6), pad 1702(2,3) to pad 1702(3,2), and pad1702(2,5) to pad (3,4). Traces 2004-3 connect pad 1702(4,2) to pad1702(5,3), pad 1702(4,4) to pad 1702(5,5), and pad 1702(4,6) to pad1702(5,1). A trace 2004-4 connects pads 1702(6,1), (6,3), and (6,5) tovia 1708-3.

With junctions 102 in a LED die 100 mounted on metalized substrate 2000,traces 2004 connect three (3) sets of junctions 102 in parallel betweenvias 1708-1 and 1708-3. The first set includes junctions 102 mounted ona pair of pads 1702(1,1) and (2,1), a pair of pads 1702(3,6) and (4,6),and a pair of pads 1702(5,1) and (6,1). The second set includesjunctions 102 mounted on a pair of pads 1702(1,3) and (2,3), a pair ofpads 1702(3,2) and (4,2), and a pair of pads 1702(5,3) and (6,3). Thethird set includes junctions 102 mounted on a pair of pads 1702(1,5) and(2,5), a pair of pads 1702(3,4) and (4,4), and a pair of pads 1702(5,5)and (6,5).

In the second (e.g., cool-white) segment, a trace 2006-1 connects via1708-4 to pads 1702(6,2), (6,4), (6,6). Traces 2006-2 connect pad1702(5,2) to pad 1702(4,1), pad 1702(5,4) to pad 1702(4,3), and pad1702(5,6) to pad (4,5). Traces 2006-3 connect pad 1702(3,1) to pad1702(2,2), pad 1702(3,3) to pad 1702(2,4), and pad 1702(3,5) to pad1702(2,6). A trace 2006-4 connects pads 1702(1,2), (1,4), and (1,6) tovia 1708-2.

With junctions 102 in a LED die 100 mounted on metalized substrate 2000,traces 2006 connect three (3) sets of junctions 102 in parallel betweenvias 1708-4 and 1708-2. The first set includes junctions 102 mounted ona pair of pads 1702(6,2) and (5,2), a pair of pads 1702(4,1) and (3,1),and a pair of pads 1702(2,2) and (1,2). The second set includesjunctions 102 mounted on a pair of pads 1702(6,4) and (5,4), a pair ofpads 1702(4,3) and (3,3), and a pair of pads 1702(2,4) and (1,4). Thethird set includes junctions 102 mounted on a pair of pads 1702(6,6) and(5,6), a pair of pads 1702(4,5) and (3,5), and a pair of pads 1702(2,6)and (1,6).

For illustrative purposes, assume growth substrate 104 has been removedfrom junctions 102 of a LED die 100 mounted on metalized substrate 1700or 2000, and cool-white phosphor layers and warm-white phosphor layersare to be formed on junctions 102 using EPD. In a first EPD process, afirst voltage is applied to the warm-white segment through via 1708-1and warm-white phosphors are electrophoretically deposited on junctions102 of the warm-white segment. During the first EPD process, a secondvoltage is applied to the cool-white segment through via 1708-4 sowarm-white phosphors are not formed on junctions 102 of the cool-whitesegment. To reduce the risk of electrical sparking between neighboringstrings, a non-zero second voltage is applied to the cool-white segment.For example, the first voltage may be 800 volts while the second voltagemay be 400 volts. To create a sharp transition in amount, type, orthickness of phosphor between the two segments, a second voltage of theopposite polarity is applied to the cool-white segment. For example, thefirst voltage may be 800 volts while the second voltage may be −400volts. Alternatively, the cool-white segment is not biased but keptfloating.

In a second EPD process, a third voltage is applied to the cool-whitesegment through via 1708-4 and cool-white phosphors areelectrophoretically deposited on junctions 102 of the cool-whitesegment. During this second EPD process, a fourth voltage is applied tothe warm-white segment through via 1708-1 so cool-white phosphors arenot formed on junctions 102 of the warm-white segment. To reduce therisk of electrical sparking between neighboring strings, a non-zerofourth voltage is applied to the warm-white segment. To create a sharptransition in amount, type, or thickness of phosphor between the twosegments, a fourth voltage of the opposite polarity is applied to thewarm-white segment. The same voltages described for the first EPDprocess may also be used for the second EPD process. Alternatively, thewarm-white segment is not biased but kept floating.

FIG. 21 is a flowchart of a method 2100 for making light-emitting devicepackage 300 in examples of the present disclosure. Method 2100 may beginin block 2102.

In block 2102, a LED die is provided. The LED die includes junctions.The LED die may be LED die 100, 1000, or 1100 (FIG. 1-2, 10, or 11). TheLED die may include wavelength converters on its growth substrate overits junctions. Block 2102 is followed by block 2104.

In block 2104, a metalized substrate is provided. The metalizedsubstrate has pads and traces connected to the pads. The metalizedsubstrate may be metalized substrate 400, 600, 800, 1700, or 2000 (FIG.4, 6, 8, 17, or 20). Block 2104 may be followed by block 2106.

In block 2106, the LED die is mounted on the metalized substrate. Forexample, the junctions are mounted on the pads of the metalizedsubstrate to create individually addressable segments. Each segment hasone or more junctions. If wavelength converters are not present in theLED die, they are formed on the growth substrate of the LED die afterthe LED die is mounted on the metalized substrate. Alternatively, thegrowth substrate of the LED die is removed and the wavelength convertersare formed on the junctions in the LED die. Block 2106 may be followedby block 2108.

In block 2108, a primary optic is mounted over the LED die.

FIG. 22 is a flowchart of a method 2200 for making a LED die in examplesof the present disclosure. Method 2200 may begin in block 2202.

In block 2202, junctions are formed that are at least partiallyelectrically insulated from each other. Block 2202 may be followed byblock 2204.

In block 2204, wavelength converters are formed. Each wavelengthconverter is located over a different junction and separated by a gapfrom neighboring wavelength converters.

The devices described above may be used in any suitable application,such as general lighting, backlighting, or specialized lightingapplications. FIG. 23 shows a system 2300 in some examples of thepresent disclosure. System 2300 includes a package 300 mounted on aprinted circuit board (PCB) 2302. Package 300 has traces to itsjunctions connected by PCB traces to one or more drivers 2304 and 2306on the PCB 2302, which are controlled by a microcontroller 2308. System2300 may be part of a headlight assembly 2310 of a motor vehicle 2312where the headlight assembly 2310 is capable of beam steering, spotreduction, highlighting and dynamic effect features. For a colorchanging package 300, system 2300 may be part of a flash 2314 for acamera 2316 in a mobile phone 2318 where the flash 2314 is capable ofcolor adjustment.

The devices described above may be light emitting pixel arrays thatsupport applications benefitting from fine-grained intensity, spatial,and temporal control of light distribution. This may include, but is notlimited to, precise spatial patterning of emitted light from pixelblocks or individual pixels. Depending on the application, emitted lightmay be spectrally distinct, adaptive over time, and/or environmentallyresponsive. The light emitting pixel arrays may provide pre-programmedlight distribution in various intensity, spatial, or temporal patterns.The emitted light may be based at least in part on received sensor dataand may be used for optical wireless communications. Associated opticsmay be distinct at a pixel, pixel block, or device level. An examplelight emitting pixel array may include a device having a commonlycontrolled central block of high intensity pixels with an associatedcommon optic, whereas edge pixels may have individual optics. Commonapplications supported by light emitting pixel arrays include cameraflashes, automotive headlights, architectural and area illumination,street lighting, and informational displays.

A light emitting pixel array may be well suited for camera flashapplications for mobile devices. Typically, an intense brief flash oflight from a high intensity LED is used to support image capture.Unfortunately, with conventional LED flashes, much of the light iswasted on illumination of areas that are already well lit or do nototherwise need to be illuminated. Use of a light emitting pixel arraymay provide controlled illumination of portions of a scene for adetermined amount of time. This may allow the camera flash to, forexample, illuminate only those areas imaged during rolling shuttercapture, provide even lighting that minimizes signal to noise ratiosacross a captured image and minimizes shadows on or across a person ortarget subject, and/or provide high contrast lighting that accentuatesshadows. If pixels of the light emitting pixel array are spectrallydistinct, color temperature of the flash lighting may be dynamicallyadjusted to provide wanted color tones or warmth.

Automotive headlights that actively illuminate only selected sections ofa roadway are also supported by light emitting pixel arrays. Usinginfrared cameras as sensors, light emitting pixel arrays activate onlythose pixels needed to illuminate the roadway while deactivating pixelsthat may dazzle pedestrians or drivers of oncoming vehicles. Inaddition, off-road pedestrians, animals, or signs may be selectivelyilluminated to improve driver environmental awareness. If pixels of thelight emitting pixel array are spectrally distinct, the colortemperature of the light may be adjusted according to respectivedaylight, twilight, or night conditions. Some pixels may be used foroptical wireless vehicle to vehicle communication.

Architectural and area illumination may also benefit from light emittingpixel arrays. Light emitting pixel arrays may be used to selectively andadaptively illuminate buildings or areas for improved visual display orto reduce lighting costs. In addition, light emitting pixel arrays maybe used to project media facades for decorative motion or video effects.In conjunction with tracking sensors and/or cameras, selectiveillumination of areas around pedestrians may be possible. Spectrallydistinct pixels may be used to adjust the color temperature of lighting,as well as support wavelength specific horticultural illumination.

Street lighting is an important application that may greatly benefitfrom use of light emitting pixel arrays. A single type of light emittingarray may be used to mimic various street light types, allowing, forexample, switching between a Type I linear street light and a Type IVsemicircular street light by appropriate activation or deactivation ofselected pixels. In addition, street lighting costs may be lowered byadjusting light beam intensity or distribution according toenvironmental conditions or time of use. For example, light intensityand area of distribution may be reduced when pedestrians are notpresent. If pixels of the light emitting pixel array are spectrallydistinct, the color temperature of the light may be adjusted accordingto respective daylight, twilight, or night conditions.

Light emitting arrays are also well suited for supporting applicationsrequiring direct or projected displays. For example, warning, emergency,or informational signs may all be displayed or projected using lightemitting arrays. This allows, for example, color changing or flashingexit signs to be projected. If a light emitting array is composed of alarge number of pixels, textual or numerical information may bepresented. Directional arrows or similar indicators may also beprovided.

Various other adaptations and combinations of features of theembodiments disclosed are within the scope of the invention. Numerousembodiments are encompassed by the following claims.

1. A method for making a light-emitting device comprising: arranging aplurality of semiconductor diodes (LEDs) on a metalized substrate toform a first group of LEDs electrically connected to each other and asecond group of LEDs electrically connected to each other, the first andsecond groups of LEDs forming a LED array; performing electrophoreticdeposition (EPD) to deposit wavelength converters on the first group ofLEDs by applying a first voltage to the first group of LEDs; andperforming EPD to deposit wavelength converters on the second group ofLEDs by applying a second voltage to the second group of LEDs.
 2. Themethod of claim 1 wherein performing EPD to deposit wavelengthconverters on the first group of LEDs comprises applying a thirdnon-zero voltage to the second group of LEDs.
 3. The method of claim 2wherein performing EPD to deposit wavelength converters on the secondgroup of LEDs comprises applying a fourth non-zero voltage to the firstgroup of LEDs.
 4. The method of claim 1 wherein the wavelengthconverters deposited on the first group of LEDs differ in compositionfrom the wavelength converters deposited on the second group of LEDs. 5.The method of claim 4 wherein the wavelength converters deposited on thefirst group of LEDs each comprise a cool-white phosphor layer, thewavelength converters deposited on the second group of LEDs eachcomprise a warm-white phosphor layer, and the LEDs are blue emittingLEDs.
 6. The method of claim 2 wherein the third non-zero voltage is avoltage with an opposite polarity to the first voltage.
 7. The method ofclaim 1 wherein LEDs in the first group of LEDs are electricallyconnected in parallel.
 8. The method of claim 1 wherein LEDs in thefirst group of LEDs are electrically connected in series.
 9. The methodof claim 1 wherein performing EPD to deposit the wavelength converterson the first group of LEDs comprises depositing the wavelengthconverters in a checkboard pattern.
 10. The method of claim 1 whereinthe first voltage is the same as the second voltage.
 11. A method formaking a light-emitting device comprising: arranging a plurality of LEDson a metalized substrate to form a first group of LEDs electricallyconnected to each other and a second group of LEDs electricallyconnected to each other, the first and second groups of LEDs forming aLED array; performing electrophoretic deposition (EPD) to depositwavelength converters on the first group of LEDs but not on the secondgroup of LEDs by applying a first voltage to the first group of LEDs.12. The method of claim 11 wherein performing EPD to deposit wavelengthconverters on the first group of LEDs comprises applying a secondnon-zero voltage to the second group of LEDs.
 13. The method of claim 12wherein the second non-zero voltage is a voltage with an oppositepolarity to the first voltage.
 14. The method of claim 11 wherein LEDsin the first group of LEDs are electrically connected in parallel. 15.The method of claim 11 wherein performing EPD to deposit the wavelengthconverters on the first group of LEDs comprises depositing thewavelength converters in a checkboard pattern.
 16. A light-emittingdevice comprising: an LED array comprising a first group of LEDselectrically connected to each other and a second group of LEDselectrically connected to each other, each LED comprising a firstsemiconductor surface, a second semiconductor surface oppositelypositioned from the first semiconductor surface, and an active region; ametalized substrate, the plurality of LEDs arranged on a metalizedsubstrate so that the first semiconductor surfaces of the LEDs areadjacent to the metalized substrate and so that the distance betweenactive regions of any two adjacent LEDs in the LED array is between 1 to100 micrometers; wavelength converters directly disposed on each of thesecond semiconductor surfaces of the first group of LEDs; and eitherwavelength converters directly disposed on each of the secondsemiconductor surfaces of the second group of LEDs, the wavelengthconverters disposed on the first group of LEDs differ in compositionfrom the wavelength converters disposed on the second group of LEDs, orno wavelength converters are disposed on the second group of LEDs. 17.The light-emitting device of claim 16 wherein the wavelength convertersdisposed on the first group of LEDs each comprise a cool-white phosphorlayer, the wavelength converters disposed on the second group of LEDseach comprise a warm-white phosphor layer, and the LEDs are blueemitting LEDs.
 18. The light-emitting device of claim 16 wherein thewavelength converters disposed on the first group of LEDs and thewavelength converters disposed on the second group of LEDs form acheckerboard pattern.
 19. The light-emitting device of claim 16 whereinwavelength converters are directly disposed on each of the secondsemiconductor surfaces of the second group of LEDs and the wavelengthconverters disposed on the first group of LEDs differ in compositionfrom the wavelength converters disposed on the second group of LEDs. 20.The light-emitting device of claim 16 further comprising a singleprimary optic comprising an overmolded silicone lens or window, anovermolded glass lens or window, a preformed silicone lens or window, ora preformed glass lens or window.